Control apparatus



Nov. 11, 1941.

R. W. HASTINGS CONTROL APPARATUS Filed March 8, 1939 INVENTOR If ROGER mamas, I BY d ATTORN Patented Nov. 11, 1941 CONTROL APPARATUS Roger W. Hastings, Springfield, Mass., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 8, 1939, Serial No. 260,517

7 Claims.

My invention relates to control apparatus and it has for an object to provide improved apparatus of this kind.

A further object of my invention is to provide improved control apparatus for refrigerating machines which is inexpensive to construct and which may be readily applied to various forms of refrigerators.

It is a further object of the invention to provide an improved control apparatus employing a snap-acting thermal device that may be adjusted to maintain different temperatures.

A still further object of the invention is to provide an improved control mechanism including a hermetically sealed switch structure and to provide for adjustment of the switch structure so that the temperatures at which the contacts are opened and closed may be varied at will and substantially independently of each other.

It is another object of the invention to provide an improved mounting for a control mechanism employing a snap-acting thermal device.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a sectional view of my improved control mechanism taken on the line I-I of Fig. 2 and includes a diagrammatic view of a domestic refrigerator having my improved control mechanism applied thereto;

Fig. 2 is a sectional view of my improved con trol mechanism taken on line II-II of Fig. 1; and,

Fig. 3 is a detail View of one of the supports for the snap-acting thermal element shown in Figs. 1 and 2.

Referring specifically to the drawing for a detailed description of my invention, numeral ll designates a hermetically sealed casing containing a control mechanism generally designated at l2. The hermetically sealed casing ll embodies a heat conducting cover member l3, preferably formed of a metal such as copper or brass and anelectrical and heat insulating base member l4, preferably formed of a material such as hard rubber or a molded plastic composition.

The base member I4 is provided with an opening IS in which a tapped metal bushing I6 is disposed. A threaded sh'a'ftfi is screwed into the metal bushing l6 and extends outwardly therefrom a considerable distance. A stop 2!) in the form of a bolt head is provided at the end of The supporting fingers I8, a detail of which is shown in Fig. 3, are molded into the base member l4. As shown in Fig. 2, three equally spaced supporting fingers l8 are provided adjacent the periphery of the base member l4. A bi-metal snap-acting disk I9 is supported by the fingers I8 and is provided with an aperture 2i in the center thereof through which the threaded shaft I1 extends.

An insulating bushing 22 is slidably mounted on the shaft l1 and a shoulder 23 thereof is held in engagementfwith the bi-metal disk l9 by a coiled spring 23. One end of the spring 21 engages a washer 30 on the bushing 22 and the other end engages a shoulder 28 in the base member l4. A movable contact member 25 is loosely mounted on the bushing 22 and is in engagement with one end of a coiled spring 24. A second shoulder 26 is provided on the bushing 22 and engages the movable contact member 25 when the switch mechanism is in th closed circuit position. Two stationary contacts 29, shown in Figs. 1 and 2, are mounted on the base member l4. Terminals 3i extend through the base member I4 and are connected to conductors 32.

A rubber cap 33 may be clamped over the hermetically sealed casing H to protect the terminals 3| and provide an opening for the conduits 32.

I have shown my invention as applied to domestic refrigerating machines in which a motor 34 drives a compressor 35 to compress refrigerant and condense the same in a condenser 36 cooled by a fan 31. The condensed refrigerant 35 is delivered through a conduit 38 to an evaporator 39, a portion of which is shown in Fig. 1, any suitable expansion device (not shown) being disposed between the condenser 36 and the evaporator 39. Vaporized refrigerant is returned to the compressor through a conduit 4|.

and closes the circuit to the motor 34 in response to the temperature of th evaporator 39, the heat conducting cover l3 of the casing ll providing for the passage of heat between the evaporator 39 and the bi-metal disk l9.

Preferably, each finger I8 is provided with a spring member 44 formed of a good heat conducting material such as phosphor-bronze and so positioned that it will contact with the metal heat conducting cover l3 when the cover I3 is in its assembled position on the base l4. The

the shaft H for a purpose hereinafter described. phosphor-bronze springs 44 provide increased heat transfer from the evaporator 39 to the interior of the sealed control mechanism 12 and to the bi-metal disk I9. This feature, however, does not form a part of the present invention and is fully disclosed and claimed in the copending application of Gerald P. Marcy, Serial No. 260,- 500, filed March 8, 1939, for Refrigeration apparatus.

In accordance with my invention, the temperatures of the evaporator 39 at which the bi-metal disk I9 respectively opens and closes the contacts 25, 29 may be varied substantially independently of each other.

If it is desired to change the temperature of the evaporator 39 at which the bi-metal disk I9 closes the contacts, the shaft i1 is screwed into or out of the tapped metal bushing It so that the stop 20 is moved either towards or away from the disk l9. When the disk i9 snaps to the open contact position (not shown) th center of the disk engages the stop 20. Therefore, if it is desired to raise the temperature of the evaporator 39 at which the disk I9 will snap to close the contacts 25, 29 the stop 20 is positioned closer to the disk 19 so that when the disk is in the open contact position its internal stress will be increased mechanically and less of a temperature change will be required to snap the disk. On the other hand, if it is desired to lower the temperature at which the evaporator 39 will snap the disk l9 to the closed contact position, the stop 20 is positioned further away from th disk I! so that the stress in the disk I9 due to mechanical force, when in the open contact position, is lessened and a greater temperature change will be required to snap the disk to the closed contact position.

When it is desired to vary the temperature at which the contacts 25, 29 are opened, the position of the bi-metal disk I9 relative to the bushing 22 is changed by moving the disk I! bodily in notches 45 provided in the fingers ll. For example, if it is desired to decrease the temperature at which the disk I! opens the contacts 25, 29 from that shown in Fig. 1, the disk I9 is bodily moved to notches nearer the bushing 22 in fingers It. The internal stresses in the bi-metal disk I9 are, therefore, increased mechanically and thus a reduction in the temperature of the disk l9 and the evaporator 39 is required to open the contacts 25, 29. On the other hand, if the bi-metal disk [9 is moved to notches 45 more remote from the bushing 22, the internal stresses in the bi-metal disk I! are decreased and the temperature necessary to open the contacts 25, 29 will b lower. Since the bushing 22 is always in contact with the center of the disk l9, as-the disk I9 is moved in the notches 45, the shoulder 23 of bushing 22 remains stationary so that only the edges of the disk I! are moved, with the result that the disk assumes eithera flatter position or a more concave position. It may then be necessary to change the position of the stop 20 to compensate for the change in position of the disk IS in the notches 45, if it isdesired to maintain the contact closing temperature the same. When the disk I! is adjusted in the manner aforesaid, only the temperature at which the evaporator 39 effects opengas such as nitrogen and the conduit 49 pinched 03', so that oxidation of contacts 25, 29 is prevented.

Another feature of my invention is the manner of sealing the hermetically sealed casing II. In order to efiect a complete hermetic seal, the base member I4 is provided with an annular notch 41 in which a gasket 48 of a resilient material such as rubber is disposed. The metal cover I3 is then disposed in its position on the base I4 and the edge thereof is rolled inwardly and downwardly, as shown at 49, by any suitable tool. This provides a very inexpensive method of hermetically sealing the casing H and also facilitates reopening the casing for repairs, after which the cover i3 may be re-rolled to again provide a hermetic seal.

From the foregoing it will be apparent that I have provided an improved switch structure of the hermetically sealed bi-metal thermostat type in which both the upper and lower temperature at which the thermostat operation may be varied independently of each other. It is also apparent that I have provided improved means for effecting such adjustments. I have also provided a very economical structure for hermetically sealing the switch structure which may be resealed after it is opened, if desired.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. A switch structure embodying electrical contacts and a bi-metal disk type thermostat for opening and closing said contacts in response to changes in temperature, a plurality of fingers retaining said bi-metal disk thermostat in snap-acting position, a stop for engaging said thermostat when in its closed contact position, and means associated with at least one of said supporting fingers affording movement of at least a portion of said bi-metal disk as an entirety as distinguished from snap-acting movement to change the travel of said disk when it snaps to the closed contact position.

2. A switch structure embodying electrical contacts and a bi-metal disk type thermostat for opening and closing said contacts in response to changes in temperature, a plurality of fingers retaining said bi-metal disk thermostat in snapacting position, a stop for engaging said thermostat when in its closed contact position, and means associated with at least one of said supporting fingers aflording movement of at least a portion of said bi-metal disk as an entirety as distinguished from snap-acting movement to change the travel of said disk when it snaps to the closed contact position, said last-mentioned means including a plurality of notches on at least one of said fingers engaging said disk and extending at an angle to the snap-acting force exerted by said disk.

3. A switch structure embodying electrical contacts and a bi-metal thermostat for opening and closing said contacts in response to changes in temperature, a supporting means for retaining said thermostat in position and a stop for engaging said thermostat when in its closed contact position, said supporting means affording movement of said bi-metal thermostat as an entirety as distinguished from snapacting movement to change the travel of the thermostat when it snaps to its closed contact position to change the temperature at which the thermostat operates to open the contacts.

4. A switch structure claimed in claim 3 wherein a second stop is adjustable to change the travel of said thermostat in its open contact position to change the temperature at which the thermostat operates to close the contacts.

5. In a control mechanism, the combination of a base member, movable and fixed electrical contacts supported on said base member, a bimetal thermostat for opening and closing said contacts disposed above said electrical contacts, means for supporting said bi-metal thermostat from said base member, said base member being provided with an opening therein, a shaft extending into said opening and freely through said thermostat, an insulating bushing slidably supported on said shaft in a position to be engaged by said thermostat and resilient means for maintaining said bushing in engagement with said thermostat, said movable electrical contact being mounted on said bushing in a position to engage said fixed contact when the thermostat moves to the closed contact position.

6. A switch structure embodying electrical contacts and a bi-metal disc type thermostat for opening and closing said contacts in response to changes in temperature, a plurality of fingers retaining said bi-metal disc thermostat in snap-acting position, a stop for engaging said thermostat when in its closed contact position, and means associated with at least one of said supporting fingers affording movement of at least a portion of said bi-m'etal disc as an entirety as distinguished from snap-acting movement to change the travel of said disc when it snaps to the closed contact position.

'7. A switch structure embodying electrical contacts and a bimetal disc type thermostat for opening and closing said contacts in response to changes in temperature, a plurality of supporting members retaining said bi-metal disc thermostat in a position afiording snap-acting movement, a stop for engaging said bi-metal thermostat when in its closed contact position, and means associated with at least one of said supporting members for changing the internal stress of the bi-metal disc independently of the stresses therein due to prevailing temperatures.

ROGER W. HASTINGS. 

